VI. PERCY ALLAN. 
The bottom chords of the 1886 type of trusses for 90 feet spans 
14” by 18” were built up of four 14” by 44” flitches, planed on all 
surfaces to ensure good butting, the whole being drawn up with 
§ inch bolts. This is a costly and undesirable design of chord, 
offering as it does, after a few years, an entrance for water 
between the flitches, causing decay, which is especially serious on 
account of the design of truss being such that the bottom chord 
cannot be renewed, thus necessitating in some cases the replacing 
- of the whole structure, which under other circumstances—with a 
few new flitches—might have lasted for several years longer. 
_ Again, some of the flitches are 53’ 6” long and, having to 
be free of heart and sapwood, are difficult to obtain, and this 
oftentimes occasioned delay in the erection of the structures, the 
simple-minded sawmill proprietor supplying all the short and 
profitable sizes in the bridge, and then pleading inability to 
supply the more costly flitches. 
The bending stress in the bottom chord of the new truss having 
been eliminated by the omission of intermediate floor beams, only 
a direct stress has to be provided for, resulting in a considerable 
reduction in the sectional area of the bottom chord, which consists 
only of two flitches 12” by 5” placed 6 inches apart, thus being 
_ always accessible to the brush, and permitting of the renewal of 
these important members ; again, the longest flitch is only 36 feet, 
a length easily procurable. 
Perhaps the most important connection in a timber truss is 
the bottom chord joint. 
Plate 5, fig. 1, shows the eover adopted for the very old types 
of truss, which can at a glance be seen to be of little assistance 
in making up the loss of section caused by the joint in the chord. 
Plate 5, fig. 2, shows the cover used in the 1886 type of 
truss; this is a much superior connection, but is expensive and 
difficult to fit. 
Plate 5, fig. 3, shows the cover adopted for the new type of 
truss. 
